The invention refers to epoxy compounds containing composition polymerizable by light for use in dental medicine and/or dentistry, consisting of one or more epoxy compounds, a plasticizer, a catalyst for hardening by ring opening, a catalyst for hardening by light and an accelerator.
It is known to prepare compositions on basis of acrylates applicable in dental medicine which can be hardened by radical polymerization using ultraviolet and visible light. These compositions have the disadvantage of shrinking strongly at hardening, and the hardened material has abrasion and solidity problems. Further it is known to prepare epoxy compounds containing compositions, which can undergo cationic polymerization with low shrinkage. In this case it is however necessary to use for such a polymerization a light source with high energy, e.g. a e-non/mercury vapor lamp, which can not be used in medical practices because of danger of combustion. Moreover, the known hardened composition does not fulfill the requirements for freedom of adhesiveness and abrasiveness. To achieve a complete hardening it is necessary to apply a thermic after-treatment, which is not practicable in the mouth of a patient.
From Minnesota Mining disclosure WO-A-98/47047 it is known to harden a composition obtained by the combination of a cyclic diepoxide, tetrahydrofurane, diphenyliodoniumhexa-fluorantimonate and camphor quinone by means of accelerators (e.g.4-dimethylaminobenzaldehyde, 4-dimethylaminophenethanol, di-hydroxyethyl-p-toluidine, ethyl-4-dimethylaminobenzoate) at wavelengths of 400 to 1000 nm. The so-obtained materials can be used as dental material. The broad scope of claim 1 of WO-A-98/47047 covers accelerators for hardening of the above compositions wherein the p-amino group of a p-aminobenzoic acid alkyl ester is substituted by one or two hydroxyalkyl groups. However, the last mentioned compounds are claimed as accelerators in a broad sense only, and there is no evidence that a compound of this group has ever been investigated or used for the acceleration of hardening.
According to the invention it has been found that the N,N-bis-hydroxyalkyl-p-aminobenzoic acid alkyl esters have an excellent efficacy as accelerators of the light induced hardening of a composition comprising one or more epoxy compounds, a plasticizer, a catalyst for ring opening and a catalyst for hardening by light.
It is therefore a purpose of the present invention to provide epoxy compounds containing compositions for use in dental medicine and/or dentistry which are free of the disadvantages of acrylate compositions, and which are hardenable by light polymerization practically without shrinkage, have a smooth, abrasion-proof surface, and which are moreover not adhesive. The surface of the hardened composition should not discolor and should inhibit bacterium deposits. Moreover, the composition does not deliver toxic substances to a cavitation during filling or on a surface during hardening.
Further, it is a purpose of the invention to provide epoxy compounds containing compositions for use in dental medicine and/or dentistry, wherein the accelerator used for hardening displays an outstanding efficacy by hardening the composition in the shortest time possible.
These purposes are achieved by the use of a polymerizable composition containing one or more epoxy compounds, a plasticizer, a catalyst for ring opening, a catalyst for hardening by daylight using as an accelerator a p-amoniobenzoic acid alkyl ester N,N-disubstituted by hydroxyalkyl groups.
The advantage of the present invention lies in the fact that a composition containing one or more epoxy compounds can be hardened using conventional dentist lamps in the shortest time possible in such a way that a polymer is obtained which is practically free of shrinkage, has an adhesive free surface, and which does not need any further after treatment.
The composition according to the invention polymerizes with a very smooth surface, by which bacteria deposits are inhibited. Unless otherwise indicated, all percentages are on a weight percentage basis in this specification.
In the composition according to the invention, the epoxy compounds can be selected from the group consisting of oligomers, which can be polymerized by cationic ring opening e.g. cycloaliphatic epoxides, cycloaliphatic diepoxides, oxetanes, oxetan-silanes, epoxilated vinyl ethers, bisphenol-A-epoxides, bisphenol-F-epoxides, bisphenol-A-F-epoxides, epoxy novolakes, phosphacenes, silikones, phosphonites, isoxazoles, ethers, thioethers, lactones and lactames, which are present in an amount of 20 to 95%, and preferably to 90% relative to the total amount of the composition.
Besides the epoxy compounds, the composition additionally contains plasticizers, which are selected from the group consisting of polyols, alkyl glycidyl esters, 1,7-diepoxy octone, 1,4-butandioldiglycidyl ester, vinylcyclohexenediol, limonendioxide, tetrahydrofurane, polytetrahydrofurane mw. 220-2000, caprolacton, glycidol, mono-, di- and multifunctional alcohols, propylenglycol, butandiol, butoxyethanol and hydroxyfonctional compounds, which are present in an amount of 1 to 30%, preferably 10%, based on the total amount of the composition.
The hardening by ring opening takes place by means of cationic catalysts, which are selected out of the group comprising ferrocenium salts, cyclic sulfonium salts, onium salts, diarylhalonium salts, aryldiazonium salts, triarylsulfonium salts, diaryliodonium salts, and aromatic and/or aliphatic iodonium salts, which are present in an amount of 0,1 to 8%, preferably 2%, based on the total weight of the composition. The hardening of the composition by daylight takes place with the aid of catalysts, which are selected out of the group comprising camphor quinone phenanthren quinone, glyoxal, 5,7 diiodo-3-butoxy-6-fluorone, biacetyl, 3,3,6,6-tetramethyl-cyclohexandione, benzil, photoinitiators of the flouron series, 3,6-dihydoxyxanthone, hydroperoxide, dibenzoylperoxide and cumolperoxide, which are present in an amount of 0.01 to 3%, preferably 0.2%, based on total weight of the composition.
The accelerators used according to the invention are p-aminobenzoic acid esters N,N-disubstituted by hydroxyalkyl groups. They can be selected from the group comprising ethyl-N,N-di-hydroxypropyl-p-aminobenzoate and ethyl-N,N-di-hydroxyethyl-p-aminobenzoate.
Especially preferred catalysts for their advantageous properties are hydroxyalkyl groups N,N-disubstituted p-amino-benzoic acid alkyl esters, such as ethyl N,N-di hydroxypropyl-p-aminobenzate, especially 4-[bis(2-hydroxypropyl)amino]benzoic acid ethylester, and ethyl N,N-dihydroxyethyl-p-amino-benzoate, especially 4-[bis(2-hydroxyethyl)amino]benzoic acid ethylester.
Likewise very useful are accelerators of the type of hydroxyalkyl (mono) or (poly)oxyalkylen group N,N-disubstituted-p-aminobenzoic acid alkyl- or alkyl (mono) or (poly)oxyalkylenesters, especially the xcfx89-ethylpoly(oxyethylen)-4-[bis{xcfx89-(2-hydroxyethyl)poly(oxyethylen)-amino]-benzoate, also known under the name PEG-25-PBA.
Surprisingly it has been found that the last mentioned accelerators are useful at the same time as light stabilizers and color stabilizers. The alkyl esters and alkyl(mono) or (poly)oxyalkylene esters of the benzoic acid mentioned in this connection comprise of course also alkyl esters and alkyl(mono) or (poly)oxyalkylen esters substituted by halogen, hydroxyl groups etc. The hydroxyalkyl groups used here for the N,N-disubstitution contain one or more hydroxyl groups, whereby the alkyl group contains 1 to 6, and preferably 1 to 4, carbon atoms.
The accelerators are present in the composition according to the invention, in an amount of 0.1 to 5%, preferably of 0.4%, based on the total weight of the composition.
In accordance with the present invention, the polymerization of the present compositions occurs by means of light with a wavelength of 340-500 nm, preferably 480 nm.
The composition according to the invention may further contain filler materials which are suitable for medical use. A useful filler material is, for example, fine-grained silicon dioxide, preferably X-ray opaque glass, like barium and strontium glass, silica glass and titanium dioxide. Such fillers may comprise 5-85% by weight, based on the total weight of the composition. Titanium dioxide, in an amount of 0.1 to 10% may be used as a sealant. In composites, silica glass and/or X-ray opaque glasses, like barium and strontium glass, can be used individually or together in an amount of 20-75%, based on the total weight of the composition. By addition of the filler materials the hardness of the polymerized composition is considerably increased.
Further, the composition may contain coloring pigments, and/or color and light stabilizers.
The preparation of the composition according to the invention is effected by mixing the components in the given amounts as described. The components are individually known or can be prepared from known starting materials in a known manner.
The following examples serve to illustrate the invention more closely without restricting its content or scope.